This disclosure relates to a reimagable and reusable medium and a method of producing the same. The reimagable and reusable medium, according to the present disclosure, is a substrate composed of a photochromic polymer and a binder polymer having a substantially similar backbone structure.
Conventional methods for producing electrophotographic reusable media entail coating a small photochromic molecule and a non-photochromic polymer binder to create a thin imaging layer of photochrome and binder on a preformed substrate, such as paper. The binder increases viscosity of the coating composition. A higher viscosity provides a thicker coating, which increases the amount of photochromic material per surface unit. An increased amount of photochromic material in the coating composition is desired for initial writability of the erasable media.
The resulting media is re-writable and reusable as a result of the reversible coloration-decoloration properties of the photochromic molecule. With conventional reusable media, ultraviolet (UV) light is used to color (or write) the photochrome in the media, and visible light and/or elevated temperatures reverse the coloration process, erasing the color of the photochrome within the media.
Conventional polymer binders such as polymethyl methacrylate (PMMA) are used in combination with photochromic monomers such as spiropyrans to form erasable media. As a result, visible images written on conventional erasable media are readable for a few hours under ambient light conditions, and are often self-erased with no effort from the user. In most cases, the self-erased erasable media are ready to be imaged again within about a day.
It is desirable, however, for the erasable media to have a longer image lifetime as well as an acceptable initial writability. It would also be desirable for an erasable medium to be readable for as long as required by the user, then erased on demand and available for subsequent re-imaging. Thus, erasable media with increased writability, longer image lifetime, and/or higher reusability as compared with conventional erasable media remain desirable.